Tractor hydraulic lift system

ABSTRACT

A tractor hydraulic lift system in which the lift system may be controlled by driveline torque, by draft sensed by one of the tractor hitch links or by a position control cam. The mechanism is arranged to permit combinations of position control with draft control and with torque control.

United States Patent 1191 Foxwell et al.

TRACTOR HYDRAULIC LIFT SYSTEM Inventors: William J. Foxwell, Troy; JamesD. Parsons, Birmingham, both of Mich.

Assignee: Ford Motor Company, Dearborn,

Mich.

Filed: June 11,1971

Appl. No.: 152,316

U.S. c1 ..172/7, 172/9 Int. Cl. ..A0lb 63/112 Field of Search ..172/7,9, 8, 10,

References Cited UNITED STATES PATENTS McKeon ..1 72/7 X [1 11 3,732,9331 51 May 15, 1973 3,653,446 4/1972 Kalmon ..172 9 x 3,613,798 10/1971Mohan et a1. ..172/9 3,241,621 3/1966 Bunting ..172/9 3,313,359 4/1967Jin 172/12 Primary ExaminerRobert E. Pulfrey Assistant Examiner-StephenC. Pellegrino A ttorney- Peter F. Hilder et a1.

[5 7] ABSTRACT A tractor hydraulic lift system in which the lift systemmay be controlled by driveline torque, by draft sensed by one of thetractor hitch links or by a position control cam. The mechanism isarranged to permit combinations of position control with draft controland with torque control.

5 Claims, 5 Drawing Figures PmmnH-w 3.732.933

SHEET 1 0F 3 HNVENTORS JO 14 J. [OZ Will MA LZA ATTORNEY J. D. PAKSO/VS1 TRACTOR HYDRAULIC LlFI SYSTEM This invention relates to tractors, andmore particularly to hydraulic lift systems for tractors.

Agricultural and general purpose tractors usually are provided with apower liftable hitch for supporting an implement mounted on or attachedto the tractor. It is usual to provide mechanism for automatic liftingor lowering of the implement in order to maintain a more or less uniformimplement draft or load on the tractor, which is measured by the forceor reaction on the top link or lower links of the tractor hitch.customarily, the force exerted on the tractor links is sensed bydisplacement of a spring, and forces above or below that se lected foroperation result in raising or lowering the hitch to bring implementdraft within the range selected. It also is usual to provide automaticheight control of the hitch, in which the hitch is maintained at anelevation corresponding to the position of a control lever, known asposition control.

US. Pat. No. 3,575,241 of Apr. 20, 1971, issued on the invention ofCharles E. McKeon, Willard G. Smith and William Lomas disclosed amechanism for sensing the torque in the drive line behind the tractortransmission and automatically adjusting the height of the implement tomaintain the torque within a selected range.

The device of the present invention, which is an improvement on theconstruction shown in that patent, provides for regulation of the heightof an implement responsive either to implement draft as sensed by thereaction on the hitch, to drive line torque or to height of the hitchabove the ground.

Among the objects of the present invention are to provide a tractorhaving means by which an attached ground-engaging implement isautomatically raised or lowered in response to drive line torque of thetractor, or, alternatively, in response to draft reaction on theimplement hitch; to provide such a tractor in which an attachedimplement can alternatively be maintained at a fixed height or position;to provide such a tractor in which the control of implement height mayreadily be selected between torque control, position control and draftcontrol; and generally to improve tractor mechanisms of the typedescribed.

Other objects, and objects relating to details and economies ofconstruction and use will be more apparent from the detailed descriptionto follow.

Our invention is clearly defined in the appended claims. In the claims,as well as in the description, parts may at times be identified byspecific names for clarity and convenience, but such nomenclature is tobe understood as having the broadest meaning consistent with the contextand with the concept of our invention as distinguished from thepertinent prior art. The best form in which we have contemplatedapplying our invention is illustrated in the accompanying drawingsforming a part of this specification in which:

FIG. 1 is a somewhat diagrammatic side elevation of a tractor accordingto the present invention, only the rear portion of the tractor beingshown.

FIG. 2 is a vertical section through the hydraulic lift cylinder coverand associated parts of the implement lift system.

FIGQ3 is a horizontal section taken generally on the line 3--3 FIG. 2.

FIG. 4 is a diagrammatic drawing showing operation of the mechanism forselecting between torque control, position control and control.

FIG. 5 is a vertical section taken through the cover and hydraulic liftsystem.

Referring now to FIG. 1, the tractor of the present invention isgenerally similar to the tractor shown in Roeder US. Pat. No. 2,631,514,having an engine 10, variable ratio transmission 11 and rear axle 12. Animplement supporting hitch 14 may comprise a pair of lower links 15 anda top link 16 mounted for limited universal movement on the centerhousing 17 of the rear axle. An implement, e.g., a plow (not shown) maybe mounted on the hitch 14.

The hitch 14 and attached implement may be raised by means of ahydraulic lift cylinder 20 mounted on the underside of the cover 21 ofthe center housing. A piston 22 within the cylinder 20, by means of ashort rod 24, operates a ram arm 25 to rotate a rock shaft 26 journaledwithin the cover 21 counterclockwise as viewed in FIG. 5 to lift theimplement.

The ends of the rock shaft 26 extend through the cover 21 and lift arms27 are fixed to the ends thereof. Lift links 29 connect the outer endsof the lift arms to the lower links 15 for lifting the links responsiveto rearward movement of the piston 22 within the lift cylinder.

A hydraulic valve 30, which may be of the spool valve type, regulatesflow of hydraulic fluid from a source of fluidunder pressure, e.g., ahydraulic pump (not shown) to the lift cylinder 20 and flow from thecylinder 20 to a sump 31 in the bottom of the center housing. Byoperating the valve 30 in one direction, fluid under pressure isadmitted to the lift cylinder 20 to raise the hitch, while operation ofthe valve in the other direction will release fluid from the liftcylinder 20 to permit the hitch l4 and supported implement to lower inresponse to force of gravity. In the neutral, intermediate position ofthe valve 30, the hydraulic fluid is trapped within the lift cylinder 20to hold the hitch in adjusted position. The tractor as thus fardescribed is well known and generally similar to the well-known Fordtractors presently sold throughout the world.

The hydraulic valve 30 for controlling raising and lowering of the hitchis operated by a servo lever 32 pivotally connected at its lower end toa control rod 34 which in turn operates the valve spool 35 of the valve30. The upper end of the lever 32 is mounted on a crank 36 journaled inthe cover 21 of the center housing/A quadrant or control lever 37mounted on the outside of the cover 21 serves to rotate the crank 36through a limited range of adjustment and thereby position the top ofthe servo lever 32. The position of the top of the servo lever 32determines the value of the torque or draft under which the tractor isto be operated or the height of the hitch in the case of positioncontrol, as will be explained.

The top link 16 of the tractor attaches to the rear of a draft plunger39 which is mounted for fore-and-aft reciprocation in the cover 21 ofthe center housing. A draft spring 40 biases the draft plunger 39towards a fixed control position, compression or tension within thetractor top link 16 compressing the spring somewhat and moving theplunger forwardly or rearwardly an amount generally proportional to thestress on the top link and thereby responsive to draft of an implementcarried on the hitch. This arrangement is generally conventional andprovides a draft signal.

A cam 41 is fixed to the hub of the ram arm 25, which in turn is fixedto the rock shaft 26. The cam 41 has a cam surface 42 which may be aspiral relative to the axis of the rock shaft. A cam follower 44 ismounted on a lever 45 which may have a generally right angleconfiguration as indicated in the drawings, the upper end of the leverbeing mounted on a fixed pivot 46 mounted in the cover 21. As the rockshaft is rotated, the cam 41 rotates with the rock shaft and causes thelever 45 to move forwardly or rearwardly as shown in FIG. 2. Inasmuch asrotation of the rock shaft raises and lowers the implement hitch bymeans of the lift arms 27 and lift links 29, the lever 45 is positionedresponsive to the height of the hitch and therefore provides forposition control of the valve through a mechanism to be described.

Torque control of the hitch is provided by a torque sensing deviceinterposed in the drive train between the tractor transmission 11 andrear wheels 47 of the tractor. Preferably, torque is sensed by acoupling 48 interposed in the driveshaft in front of the rear axle,which may be as shown and described in said US. Pat. No. 3,575,241. Sucha coupling has a coupling half displaceable responsive to torque andconnected with a rod 49 leading rearwardly. The rod 49 is displacedvarying amounts responsive to the amount of driveline torque and isconnected to provide torque control of the valve 30 by a mechanism to bedescribed.

The valve 30 may be operated selectively responsive to driveline torque,position control or draft control, or a combination of torque or draftcontrol with position control. Referring to FIG. 2, a rail 50 has itsupper end supported by a pivot 51 mounted on the lower, rear end portionof the lever and its lower end pivotally connected to the rear end ofthe rod 49 extending from the torque sensing unit. A spring 52 biasesthe upper end of the rail rearwardly to hold the cam follower 44 againstthe cam surface 42. The upper end of the rail 50 is moved forwardly andrearwardly responsive to position control, while the lower end of therail is moved forwardly and rearwardly responsive to torque in the driveline. The lever 45 is attached to an ofi'set portion 54 of the rail.50,see FIG. 3, and the forward edge 54 of the rail is given an arcuate formfor at least a portion of its length, the center of are being located ata pivot 55 located in an intermediate portion of the servo lever 32.

A selector rod 56 is supported on the pivot 55 and has a bifurcated rearend 57 supporting a roller 59 (see FIG. 3) adapted to move along thearcuate forward edge 54 of the rail 50. Preferably, the bifurcated end57 projects on both sides of the rail to maintain the roller 59 on therail. A lever 60 fixed to a pivot 61 journaled in the lift cover and alink 62 serve to support the rear end of the selector rod 56 in adjustedposition along the rail 50. A hand lever 63 on the outside of the centerhousing cover 21 serves as a means for manually adjusting the positionof the selector rod.

Inasmuch as the lever 45 is connected to the offset portion 54 of therail 50, the arcuate edge of the rail is clear to receive the selectorrod 56 and when the rod is positioned as shown in the drawings with therear end of the rod opposite the pivot 51, the selector rod will beacted on solely in response to the lever 45 which is actuated responsiveto height of the hitch (position control). As the selector rod 56 ismoved downwardly along the rail, it reflects a combination of positioncontrol and torque control sensed by the coupling in the drive line.Preferably, the movement towards the connection of the rod 49 is limitedso as to feed in some position control in order to cut off hydraulicflow through the valve 30 and prevent overcorrecting and hunting thatmight occur under only torque control. The selector rod 56 may be lockedin any of several different positions along the rail 50 to selectdifferent ratios of torque control and position control.

A second rail 64 having an arcuate forward edge is located above and incontinuation of the rail 50, the lower end of the rail 64 having anoffset portion 65 received and supported by the pivot 51 on the rear endof lever 45 so as to move the lower end of the rail 64 together with theupper end of the rail 50 in response to height of the hitch (positioncontrol).

The upper end of the second rail 64 is supported by a pin 65 received inan offset portion of the rail 64 and connected by a link 66 with theforward or inner end of the draft sensing plunger 39. The arrangement issuch that position control sensing is fed into the lower end of the rail64 and draft control sensing is fed into the upper end. The selector rod56 may be swung upwardly from engagement with the lower rail 50 andpositioned along the upper rail 64, at which time a combination ofposition control and draft control will be sensed. If the selector rodis swung to the top of the upper rail 64 opposite the pin 66, the rodwill be actuated solely by movement of the draft sensing plunger 39.

The selector rod 56 is mounted on the servo lever 32 by a block 67slidingly receiving the rod and pivotally mounted on the servo lever. Asnap ring 69 on the forward end of the selector rod limits its rearwardmovement in the block 67 and an override spring 70 mounted on the rodbiases the snap ring 69 against the block. This override construction,which is well known, protects the linkage against damage if the senseddraft or torque changes rapidly so as to tend to move the valve spool 35beyond its range of movement and also permits the piston within thehydraulic lift cylinder 20 to engage the servo lever 32 at top of liftand force it rearwardly a small amount to restore the valve 30 toneutral position and cut off flow of hydraulic fluid to the liftcylinder 20.

Referring to FIG. 4, the selector rod 56 may be move along the upperrail 64 from the top where it is actuated solely responsive to draft tothe upper end of the lower rail 50 where it is actuated solelyresponsive to position of the hitch and to the lower end of its travelwhere it is actuated primarily responsive to driveline torque withsufficient position control to obtain cutoff of signal. In theintermediate positions, the selector rod 56 is actuated by combinationsof torque and position control or draft and position control.

We claim:

1. In a tractor having an engine, a transmission, ground driving wheels,a drive train extending between the transmission and ground drivingwheels, an implement supporting hitch, a source of hydraulic fluid underpressure, a lift cylinder for controlling the height of the implementsupporting hitch, and a control valve for regulating admission of fluidto and release of fluid from said cylinder, the improvement comprising:

a servo-lever means coupled to saidcontrol valve,

a draft sensing means coupled to the servo-lever means through aselector rod to actuate the control valve to raise or lower theimplement supporting hitch in response to deviations from apredetermined draft load on the tractor,

a torque-sensing means in the drive train coupled to theservo-levermeans flirough the selector rod to actuate the control valveto raise or lower the implement supporting hitch in response todeviations in drive line torque above or below a predetermined norm,

and a control means coupled to the servo-lever means to pre-set thecontrol valve to automatically maintain the height of the implementhitch at a predetermined setting when the draft and torque conditionsare at the desired norm.

2. In a tractor according to claim 1, in which:

a selector rod movement programming means is interposed between theselector rod and the draft and torque-sensing means,

and a selector rod positioning means coupled to the selector rod isoperable to position the latter relative to the programming means sothat the selector rod is responsive to a resultant movement of thesensing means and the setting of the hitch height control means.

3. In a tractor according to claim 2, in which:

the programming means comprises a first profiled elongated memberpivotally supported on a part of the draft sensing means and a secondprofiled member pivotally supported on a part of the torque sensingmeans,

the first profiled member being movable in response to draft-sensingdeviations as modified by hitch height setting to thereby vary thedegree of actuation of the control valve by the selector rod,

and the second profiled member being movable in response totorque-sensing deviations as modified by hitch height setting to therebyvary the degree of actuation of the control rod by the selector rod.

4. In a tractor according to claim 3, in which: the profiled members arepivotally connected to each other at their ends opposite their pivotallysupported ends,

the selector rod when positioned opposite the pivotal connection beingin a neutral position relative to the draft sensing means ancl thetorque sensing means.

5. In a tractor according to claim 4, in which:

the first and second profiled members lie in end to end relationship andprovide a control surface lying generally in a circular are about apivot located intermediate the ends of the servo-lever means,

the selector rod being swingable about the last mentioned pivot alongsaid arc.

1. In a tractor having an engine, a transmission, ground driving wheels,a drive train extending between the transmission and ground drivingwheels, an implement supporting hitch, a source of hydraulic fluid underpressure, a lift cylinder for controlling the height of the implementsupporting hitch, and a control valve for regulating admission of fluidto and release of fluid from said cylinder, the improvement comprising:a servo-lever means coupled to said control valve, a draft sensing meanscoupled to the servo-lever means through a selector rod to actuate thecontrol valve to raise or lower the implement supporting hitch inresponse to deviations from a predetermined draft load on the tractor, atorque-sensing means in the drive train coupled to the servolever meansthrough the selector rod to actuate the control valve to raise or lowerthe implement supporting hitch in response to deviations in drive linetorque above or below a predetermined norm, and a control means coupledto the servo-lever means to pre-set the control valve to automaticallymaintain the height of the implement hitch at a predetermined settingwhen the draft and torque conditions are at the desired norm.
 2. In atractor according to claim 1, in which: a selector rod movementprogramming means is interposed between the selector rod and the draftand torque-sensing means, and a selector rod positioning means coupledto the selector rod is operable to position the latter relative to theprogramming means so that the selector rod is responsive to a resultantmovement of the sensing means and the setting of the hitch heightcontrol means.
 3. In a tractor according to claim 2, in which: theprogramming means comprises a first profiled elongated member pivotallysupported on a part Of the draft sensing means and a second profiledmember pivotally supported on a part of the torque sensing means, thefirst profiled member being movable in response to draft-sensingdeviations as modified by hitch height setting to thereby vary thedegree of actuation of the control valve by the selector rod, and thesecond profiled member being movable in response to torque-sensingdeviations as modified by hitch height setting to thereby vary thedegree of actuation of the control rod by the selector rod.
 4. In atractor according to claim 3, in which: the profiled members arepivotally connected to each other at their ends opposite their pivotallysupported ends, the selector rod when positioned opposite the pivotalconnection being in a neutral position relative to the draft sensingmeans and the torque sensing means.
 5. In a tractor according to claim4, in which: the first and second profiled members lie in end to endrelationship and provide a control surface lying generally in a circulararc about a pivot located intermediate the ends of the servo-levermeans, the selector rod being swingable about the last mentioned pivotalong said arc.